Laminated magnetic core



July 10, 1951 c. P. HAYES uumman mam-1c coma Filed Dec. 51, 1948 Inventor Charles F? Hayes,

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Patented July 10, 1951 LAMINATED MAGNETIC CORE Charles P. Hayes, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application December 31, 1948, Serial No. 68,557

1 Claim. 1

This invention relates to magnetic cores, and it has for an object an improved method of filling a gap in such cores with a subsequently solidified viscous liquid filler.

It is common practice to provide magnetic cores for stationary induction apparatus such as transformers and reactors with a suitably located gap so as to produce desired electromagnetic characteristics. Often the gap length or separation is quite small so that with the usual relatively high flux density at which modern apparatus of this kind operates relatively large forces are developed between the gap faces. Due to the pulsating nature of these forces, vibration of the core parts in the vicinity of the gap often results, and at the usual commercial frequencies such vibration will frequently produce an objectionable amount of noise. In order to minimize such noise it has been proposed to insert a subsequently hardened liquid filler or cement into the gap. Such filler will produce a mechanically strong separator between the edges of the usual laminations which make up the gap faces and will thus substantially prevent the magnetic force from vibrating them. However, it has been found very dimcult, if not impossible, completely to fill such narrow gaps with a viscous liquid.

In accordance with this invention, there is provided a header or feeder passageway in the form of a slot which runs through the core ad- Jacent to and in communication with one face of the gap and which has a large cross section relative to the gap spacing. In this way the viscous filler liquid can be relatively easily inserted into the feeder slot under pressure, and it will first completely fill the slot lengthwise and will then spread transversely so as to completely fill the narrow gap.

Another object of the invention is to provide a magnetic core construction which possesses a low vibratory noise level.

It is a further object of this invention to provide a magnetic core construction which allows for simple application of a cement or filler.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claim.

In the drawing Fig. l is a perspective view of a high reactance two-lamp fluorescent ballast core which incorporates a particular embodiment of the invention; Fig. 2 is a perspective view having a partially cutaway section showing a preferred method of applying the viscous fluid;

Figs. 3 and 4 are detail plan views of alternative constructions of the invention.

Referring now to the drawing, there is shown in Fig. 1 by way of example, a high reactance two-lamp fluorescent ballast core I which is the subject of the patent application Serial No. 68,546, filed December 31, 1948, which is assigned to the same assignee as the present. invention. The core I is constructed of three main sections; a central core leg 2 made up of stacked substantially I-shaped laminations. and two outer core sections 3 and 4 constructed from stacked four-legged E-shaped laminations. The sections 2, 3 and 4 of the ballast core I are bound firmly together at the ends by any suitable clamping means. (Such clamping means is not shown in the drawing.) The inner legs 5, 6, I and 8 of the E-shaped core sections 3 and 4 are separated from the central core leg 2 by the narrow air gaps 9, HI, II and I2, and the outer legs I! and I4 of the E-shaped core sections 3 and 4 are separated from the central core leg 2 by the narrow air gapsli and I6. In this particular application of the invention it is desired that the air gaps 9, l0, H, l2, l5 and It be filled with a binding cement to prevent the vibration of the projections 5, 6, I, 8, I3 and I4. Notches are punched in each of the laminations forming the central core leg 2 and when the laminations are stacked they present feeder or header slots l'l running the entire height of the stacked laminations.

A preferred method of applying the sealing cement or filler is shown in Fig. 2. In this illustration one header I! is shown enlarged and a section of the core I (e. g., the inner leg 1) is shown partially cutaway. A plate I8 of metal or any suitable material may be used to block the openin is of the header ll. Another plate 20 having a cylindrical nipple 2| which has an orifice 22 cooperating with the opening 23 of the header I1 is mounted on the other side of the core I. Thus the viscous fluid, which subsequently hardens, may be forced, under pressure, through the orifice 22 into the header l1. As can be seen in Fig. 2, as the header H is filled the viscous fluid is forced into the air gap space H and is metered uniformly throughout the height of the header l'l.

Fig. 3 illustrates in plan view a detailed portion of an alternative construction of this invention in which the notch 24 is not formed in the central core leg 25 but in the legs, one leg 28 is shown, of the E-shaped core sections.

A narrow restricted opening 21 is provided for the notch 28 in the alternative construction shown in detail in Fig. 4. This restricted opening 21 allows for a more even distribution of viscous filler since the fluid must be under higher pressure to flow through the opening 27. bviously, the notch 28 and the opening 27 may be in the central core leg 29 instead of the projecting leg .30.

It'should be noted that the viscous fluid previously referred to is in no way limited to one having cementing qualities.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departin from the invention and, therefore, it is aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

A laminated magnetic core for stationary electrical induction apparatus comprising, in combination, a plurality of individual laminated core sections in edgewise contact at a plurality of separated places thereon where the sections have complimentary shaped interfitting surfaces so as to form a closed magnetic circuit with a plurality of joints, integral legs on at least one 4 of said sections extending toward another of said sections so as to form magnetically short air gaps therebetween, header passageways extending completely through one of said sections transversely of its laminations, said header passageways being disposed entirely on one side of said air gaps and in open communication with said air gaps throughout the length of said header passageways, said header passageways having substantially greater transverse dimensions than the magnetic length of said gaps, and a hardened liquid completely filling said header passageways and air gaps.

CHARLES P. HAYES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,748,993 Purdy Mar. 4, 1930 1,783,050 Merrill Nov. 25, 1930 2,400,891 Sigmund May 28, 1946 FOREIGN PATENTS Number Country Date 571,198 Great Britain Aug. 10, 1945 

